Diagnostic Accuracy of Furosemide Stress Test and Cystatin-C for Predicting Acute Kidney Injury Progression in Children: A Prospective Cohort Study.

Objectives: To evaluate the predictive ability of furosemide stress test (FST), serum and urine cystatin-C in identifying progressive acute kidney injury (AKI) and the need for kidney replacement therapy (KRT).

Methods: Children aged one month to 18 y admitted in the pediatric intensive care unit (PICU) with Kidney Diseases Improving Global Outcomes (KDIGO) stage-1/2 AKI were enrolled. FST and serum and urine cystatin-C levels were performed and analyzed. The primary outcome was progression to stage-3 AKI. Secondary outcomes included comparing predictive ability of FST vs. cystatin-C for stage-3 AKI and need for KRT, adverse effects, length of hospital stay and mortality.

Results: Of the 41 children enrolled, seven (17.07%) progressed to KDIGO stage-3 AKI. Four children were furosemide non-responders at 2 h and five at 6 h post-FST. The sensitivity, specificity and area under the receiver operating characteristic curve (AUROC) of FST at 2 h were 57.14%, 100% and 0.84 (p = 0.01), and at 6 h were 71.43%, 100% and 0.87 (p < 0.001), respectively. Urine cystatin-C was positive in 20 (48.78%) children, of which seven progressed to stage-3 AKI [sensitivity- 100%, specificity- 61.76%, AUROC- 0.91 (p = 0.003)]. Five of nine children with positive serum cystatin-C progressed to stage-3 AKI [sensitivity- 71.43%, specificity- 88.24%, AUROC- 0.75 (p = 0.08)]. All FST non-responders progressed to undergo KRT showing sensitivity and specificity of 66.67% and 100% at 2 h (AUROC- 0.87) and 85% and 100% at 6 h (AUROC- 0.89) respectively.

Conclusions: FST is a simple bedside tool with robust predictive value in detecting kidney impairment progression in children and can be utilized in PICU for assessing tubular dysfunction. The diagnostic accuracy of FST was comparable to that of urine and serum cystatin-C. Further studies can be done on a larger cohort for better generalizability.